pub fn get_or_make_migration(
  name: String,
  migrations: Dict(String, Migration),
  next: fn(Migration) -> Result(#(String, Migration), Error),
) -> Result(#(String, Migration), Error)

pub fn validate_direction(
  direction: String,
  next: fn(String) -> Result(#(String, Migration), Error),
) -> Result(#(String, Migration), Error)